General purpose cache buster ( after build ), append checksum to <script src="..."> and <link ref="...">, cache bust js & css in any build system

after-build-cache-bust.js

#!/usr/bin/env node
const INDEX_FILE_NAME = './www/index.html';
const fs = require('fs');
const path = require('path');
const crypto = require('crypto');

function checksum(str, algorithm, encoding) {
  return crypto
    .createHash(algorithm || 'md5')
    .update(str, 'utf8')
    .digest(encoding || 'hex')
}

const fileOptions = { encoding: "utf8" };
var indexContents = fs.readFileSync(INDEX_FILE_NAME, fileOptions);

function addCacheBuster(regexp) {
  indexContents = indexContents.replace(regexp,
    function (_, before, fname, after) {
      if (fname.indexOf('?') >= 0) {
        fname = fname.substring(0, fname.indexOf('?'))
      }
      var fpath = path.join(path.dirname(INDEX_FILE_NAME), fname);
      var cs = checksum(fs.readFileSync(fpath, fileOptions), 'sha1');
      return before + fname + "?" + cs + after;
    });
}

// add cache buster for js
addCacheBuster(/(<script .*?src\s*=\s*['"]\s*)(.+?)(\s*['"].*?>)/img);

// add cache buster for css
addCacheBuster(/(<link .*?href\s*=\s*['"]\s*)(.+?)(\s*['"].*?>)/img);

fs.writeFileSync(INDEX_FILE_NAME, indexContents, fileOptions);